In recent years, many different techniques for the fast production of three-dimensional models have been developed for industrial use. These are sometimes referred to as rapid prototyping and manufacturing (“RP&M”) techniques. In general, rapid prototyping and manufacturing techniques build three-dimensional objects layer by layer from a working medium utilizing a sliced data set representing cross-sections of the object to be formed. Typically, an object representation is initially provided by a Computer Aided Design (CAD) system.
Stereolithography, presently the most common RP&M technique, may be defined as a technique for the automated fabrication of three-dimensional objects from a fluid-like material utilizing selective exposure of layers of the material at a working surface to solidify and adhere successive layers of the object (i.e. laminae). In stereolithography, data representing the three-dimensional object is input as, or converted into, two-dimensional layer data representing cross-sections of the object. Layers of material are successively formed and selectively transformed or solidified (i.e. cured) using a computer controlled laser beam of ultraviolet light (UV) into successive laminae according to the two-dimensional layer data. During transformation, the successive laminae are bonded to previously formed laminae to allow integral formation of the three-dimensional object. More recent designs have employed the use of visible light to initiate the polymerization reaction to cure the photopolymer build material that is commonly referred to as resin.
Stereolithography represents an unprecedented way to quickly make complex or simple parts without tooling. Since this technology depends on using a computer to generate its cross-sectional patterns, there is a natural data link to CAD/CAM. Such systems have encountered and had to overcome difficulties relating to shrinkage, curl and other distortions, as well as resolution, accuracy, and difficulties in producing certain object shapes.
Although stereolithography has shown itself to be an effective technique for forming three-dimensional objects, various improvements addressing the technology's difficulties and expanding the potential manufacturing applications have been desired for some time. Many improvements have addressed the aforementioned difficulties and have been made to object accuracy, speed and appearance of the build object over the years. A recent area of expansion of stereolithographic applications has been into the area of hearing aid shell manufacturing where digital data of a patient's ear is used to create a customized hearing aid shell. This is done on a large scale with as many as 160 hearing aid shells being manufactured in a single build using a stereolithography system. Many patients have two hearing aid shells made, one for each ear. Other patients require only a single hearing aid shell. Regardless, a convention has arisen among some manufacturers to color code the hearing aid shells according to which ear in which the shell is to be used. With the advent of biocompatible colored resins or build materials, a need has arisen for the ability to manufacture in a single build cycle hearing aid shells for both the left and the right ears. This requires the use of at least two separate vats within the context of the traditional stereolithography systems. Therefore there is the need for a stereolithography system to accommodate a second vat or resin material container so that hearing aid shells of two different colors can be manufactured in a single build cycle. Further, there is a need to permit easy change over of vats in a stereolithographic system between one and two vats or simply to be able to replace an existing vat.
These problems are solved in the design of the present invention.